U.S. patent number 6,460,802 [Application Number 09/660,784] was granted by the patent office on 2002-10-08 for helicopter propulsion and control system.
This patent grant is currently assigned to Airscooter Corporation. Invention is credited to Elwood G. Norris.
United States Patent |
6,460,802 |
Norris |
October 8, 2002 |
Helicopter propulsion and control system
Abstract
A helicopter propulsion and control system configured for
actuating a helicopter airframe according to control inputs of an
operator, comprising a counter-rotating rotor set tiltably coupled
to the airframe at a first location, the rotor set having a
downward thrust vector and a power assembly configured to actuate
the counter-rotating rotor set, having a center of gravity, and
being fixedly coupled to the rotor set so as to be tiltable
therewith, the center of gravity of said power assembly being
disposed below the first location where the rotor set is tiltably
coupled to the airframe and a control actuator operatively coupled
between the power assembly and the airframe to enable the center of
gravity of the airframe to move with respect to the center of
gravity of the power assembly, and with respect to the thrust
vector of the rotor set, whereby pitch and roll of the airframe are
controllable by the operator.
Inventors: |
Norris; Elwood G. (Poway,
CA) |
Assignee: |
Airscooter Corporation
(Henderson, NV)
|
Family
ID: |
24650944 |
Appl.
No.: |
09/660,784 |
Filed: |
September 13, 2000 |
Current U.S.
Class: |
244/17.11;
244/17.23 |
Current CPC
Class: |
B64C
27/10 (20130101); B64C 27/14 (20130101); B64C
27/52 (20130101) |
Current International
Class: |
B64C
27/10 (20060101); B64C 27/14 (20060101); B64C
27/52 (20060101); B64C 27/00 (20060101); B64C
027/52 () |
Field of
Search: |
;244/17.11,17.19,17.25,17.23,17.27,6 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Cox Model Helicopter, "Attack Cobra", date unknown (see
attached)..
|
Primary Examiner: Poon; Peter M.
Assistant Examiner: Collins; Timothy D
Attorney, Agent or Firm: Thorpe North & Western LLP
Claims
What is claimed is:
1. A helicopter propulsion and control system configured for
actuating a helicopter airframe having a center of gravity
according to control inputs of an operator, comprising: a
counter-rotating rotor set tiltably coupled to the airframe at a
first location, the rotor set having a downward thrust vector; a
power assembly configured to actuate the counter-rotating rotor
set, having a center of gravity, and being fixedly coupled to the
rotor set so as to tilt therewith, the center of gravity of said
power assembly being disposed below the first location where the
rotor set is tiltably coupled to the airframe; a control actuator
operatively coupled between the power assembly and the airframe to
enable the center of gravity of the airframe to move with respect
to the center of gravity of the power assembly, and with respect to
the thrust vector of the rotor set, whereby pitch and roll of the
airframe are controllable by the operator.
2. A system in accordance with claim 1, further comprising an
airfoil disposed so as to be in downwash of said rotor set, said
airfoil cooperating with the downwash of the rotor set to create a
controllable lateral thrust vector; an airfoil control actuator
operatively coupled between the airfoil and the airframe, to change
the orientation of the airfoil so as to orient the sideways thrust
vector according to control inputs of the operator, whereby yaw of
the airframe is controllable by the operator.
3. A system in accordance with claim 1, wherein said power assembly
further comprises: a prime mover; a gear set.
4. A system in accordance with claim 3, wherein the prime mover is
an electric motor.
5. A system in accordance with claim 3, wherein the prime mover is
an internal combustion engine.
6. A system in accordance with claim 3, wherein the prime mover is
a turbomachine.
7. A system in accordance with claim 3, wherein the gear set
comprises a reduction gear set.
8. A system in accordance with claim 7, wherein the gear set
comprises a planetary reduction gear set.
9. A system in accordance with claim 3, wherein the gear set
comprises a bevel gear set.
10. A system in accordance with claim 9, wherein the bevel gear set
comprises a single shaft rotation input and a dual counter-rotation
shaft output oriented orthogonal to the input.
11. A system in accordance with claim 1, wherein the power assembly
is rotatable with respect to the airframe.
12. A system in accordance with claim 11, wherein the power r
assembly has a single output shaft, and a first rotor of the
counter rotating rotor set is attached to the power assembly
rotating in a first direction and a second rotor of the counter
rotating rotor set is attached to the single output shaft and
rotates in the opposite direction.
13. A system in accordance with claim 12, wherein the power
assembly comprises: a motor; a reduction gear set.
14. A system in accordance with claim 13, whereby a relative
rotational speed of the counter-rotating rotors is less than a
speed of the motor.
15. A system in accordance with claim 1, wherein the operator is
human.
16. A system in accordance with claim 15, wherein the operator
remotely pilots the helicopter, and the system further comprises a
transmitter and a receiver cooperating with the actuator disposed
between the airframe and the power assembly to provide control
inputs.
17. A system in accordance with claim 15, wherein the operator
pilots the helicopter onboard the airframe, and wherein the
helicopter system further comprises controls actuatable by the
operator carried by the airframe.
18. A system in accordance with claim 1, wherein the actuator
disposed between the power assembly and the airframe further
comprises; a pitch actuator disposed to tilt the rotor set and
power assembly in a first direction to control pitch; and a roll
actuator disposed to tilt the rotor set and power assembly in a
second direction to control roll.
19. A system in accordance with claim 18, further comprising: an
airfoil disposed so as to be in downwash of said rotor set, said
airfoil cooperating with the downwash of the rotor set to create a
controllable sideways thrust vector; an airfoil control actuator
operatively coupled between the airfoil and the airframe,
configured to change the orientation of the airfoil so as to orient
the sideways thrust vector according to control inputs of the
operator, whereby yaw of the airframe is controllable by the
operator.
20. A system in accordance with claim 19, wherein said power
assembly further comprises: a prime mover; a gear set; a first
rotor output shaft rotating in a first direction; a second rotor
output shaft rotating in a second direction opposite the first
direction;
and wherein the prime mover powers the rotor set through the gear
set, the gear set transferring power to the first and second output
shafts, and the counter-rotating rotor set being powered by the
first and second output shafts.
21. A helicopter propulsion and control system configured for
actuating a helicopter airframe having a center of gravity
according to control inputs of an operator, comprising: a
counter-rotating rotor set tiltably coupled to the airframe at a
first location, the rotor set having a downward thrust vector; a
power assembly configured to actuate the counter-rotating rotor
set, having a center of gravity below the first location, the power
assembly being fixedly coupled to the rotor set so as to tilt
therewith; a rotor control actuator operatively coupled between the
power assembly and the airframe; whereby the center of gravity of
the airframe is movable with respect to the center of gravity of
the power assembly, and with respect to the thrust vector of the
rotor set, whereby pitch and roll of the airframe are controllable
by the operator; an airfoil disposed so as to be in downwash of
said rotor set, said airfoil cooperating with the downwash of the
rotor set to create a controllable sideways thrust vector; an
airfoil control actuator operatively coupled between the airfoil
and the airframe, configured to change the orientation of the
airfoil so as to orient the sideways thrust vector according to
control inputs of the operator, whereby yaw of the airframe is
controllable by the operator; and a power controller operatively
connected to the power assembly to enable control of power output
to the counter-rotating rotor set, whereby the magnitude of the
thrust vector of the rotor set can be controlled.
22. A system in accordance with claim 21, wherein said power
assembly further comprises: a prime mover having a prime mover
output shaft; and a gear set operatively coupled to the prime mover
output shaft; a first output shaft operatively coupled to the gear
set, rotating in a first direction operatively coupled to a first
rotor of the counter-rotating rotor set.
23. A system in accordance with claim 22, wherein a second rotor of
the counter-rotating rotor set is operatively connected to the
power assembly.
24. A system in accordance with claim 22, further comprising a
second output shaft operatively coupled to the gear set, rotating
in a second opposite the direction of rotation of the first output
shaft, operatively coupled to a second rotor of the
counter-rotating rotor set.
25. A system in accordance with claim 21, wherein the operator is
human.
26. A system in accordance with claim 25, further comprising: a
receiver carried by the airframe and operatively connected to the
power controller and the rotor control actuator and airfoil
actuator; and, a transmitter, whereby the helicopter is remotely
controlled.
27. A system in accordance with claim 21, wherein the operator is a
programable electronic guidance and control system operatively
connected to the power controller and the rotor control and airfoil
actuators, whereby the helicopter is substantially
self-controlled.
28. A system in accordance with claim 21, wherein the magnitude of
the thrust vector of the rotor set is controllable solely by
variation of the speed of rotation of the counter-rotating rotor
set.
29. A helicopter propulsion and control system configured for
actuating a helicopter, the helicopter having an airframe having a
center of gravity, according to control inputs of an operator,
comprising: a counter-rotating rotor set tiltably coupled to the
airframe at a first location, the rotor set having a downward
thrust vector; a power assembly configured to actuate the
counter-rotating rotor set, having a center of gravity below the
first location, the power assembly being fixedly coupled to the
rotor set so as to tilt therewith, said power assembly further
comprising: a prime mover; a gear set; a first output shaft; a
second output shaft, the first and second output shafts being
operatively connected to a first and second rotor of the
counter-rotating rotor set and to the gear set, power from the
prime mover thereby being transferred to the counter-rotating rotor
set; a rotor control actuator operatively coupled between the power
assembly and the airframe; whereby the center of gravity of the
airframe is movable with respect to the center of gravity of the
power assembly, and with respect to the thrust vector of the rotor
set, whereby pitch and roll of the airframe are controllable by the
operator; an airfoil disposed so as to be in downwash of said rotor
set, said airfoil cooperating with the downwash of the rotor set to
create a controllable sideways thrust vector; an airfoil control
actuator operatively coupled between the airfoil and the airframe,
configured to change the orientation of the airfoil so as to orient
the sideways thrust vector according to control inputs of the
operator, whereby yaw of the airframe is controllable by the
operator; and a power controller operatively connected to the power
assembly to enable control of power output to the counter-rotating
rotor set, whereby the magnitude of the thrust vector of the rotor
set can be controlled.
30. A system in accordance with claim 29, wherein the prime mover
comprises an electric motor.
31. A system in accordance with claim 30, wherein the rotor control
actuator further comprises: a pitch actuator; and a roll actuator;
each being operatively connected between the power assembly and the
airframe.
32. A system in accordance with claim 33, further comprising a
receiver operatively connected with the power controller and the
roll, pitch, and airfoil actuators, whereby the helicopter is
remotely controllable by the operator.
33. A helicopter propulsion and control system configured for
actuating a helicopter airframe according to control inputs of an
operator, comprising: a counter-rotating rotor set tiltably coupled
to the airframe, the rotor set having a downward thrust vector and
an axis of rotation; a power assembly configured to actuate the
counter-rotating rotor set, having a center of gravity, and being
fixedly coupled to the rotor set so as to tilt therewith with
respect to the airframe, and rotatable with respect to the airframe
about an axis substantially parallel to the axis of rotation of the
rotor set; a control actuator operatively coupled between the power
assembly and the airframe to enable a center of gravity of the
airframe to move with respect to the center of gravity of the power
assembly, and with respect to the thrust vector of the rotor set,
whereby pitch and roll of the airframe are controllable by the
operator.
34. A system in accordance with claim 33, wherein the power
assembly has an output shaft, and a first rotor of the counter
rotating rotor set is attached to the power assembly, the power
assembly and first rotor rotating in a first direction and a second
rotor of the counter rotating rotor set is attached to the output
shaft and rotates in the opposite direction.
35. A system in accordance with claim 34, wherein the power
assembly comprises: a motor; a reduction gear set.
36. A system in accordance with claim 35, whereby a relative
rotational speed of the counter-rotating rotors is less than a
speed of the motor.
37. A system in accordance with claim 34, further comprising
coaxial drive shafts comprising an inner drive shaft and an outer
drive shaft, and wherein the output shaft comprises the inner drive
shaft.
38. A system in accordance with claim 34, further comprising
coaxial drive shafts comprising an inner drive shaft and an outer
drive shaft, and wherein the output shaft comprises an outer drive
shaft.
Description
BACKGROUND OF THE INVENTION
The invention relates to helicopter power and flight control
systems. More particularly the invention relates to simplified
propulsion and flight control systems incorporated in a coaxial
helicopter vehicle.
Coaxial helicopters have been known for many years. However,
because of complexities involved in the control of the cyclic and
the collective pitch of rotor blades in a coaxial configuration to
give roll, pitch and yaw control, development of this type of
aircraft has heretofore been limited. Conventional single rotor
designs, having a tail rotor for counteracting the tendency of the
airframe to turn with respect to the rotor, and for yaw control,
predominate. Nevertheless historically several successful coaxial
designs have been developed, for example, by Nikolai Kamov and the
Kamov design bureau of the former Soviet Union. The Kamov
organization continues to produce coaxial helicopters in the
Russian Federation. Other coaxial designs exist, for example a
small coaxial pilotless craft developed by United Technologies
Corporation, of Hartford Conn. An example of a control system for
this later craft is disclosed in U.S. Pat. No. 5,058,824.
An alternative to control of coaxial helicopters by control of the
pitch of the blades alone is to make the axis of rotation of the
coaxial rotor set tiltable with respect to the airframe, which
allows pitch and roll control by shifting the weight of the
aircraft with respect to a thrust vector of the coaxial rotor set.
Such a system is known, for example that disclosed in U.S. Pat. No.
5,791,592, issued Aug. 11, 1998 to Nolan, et al. Yaw control in the
Nolan device is by means of two sets of airfoils which are tiltable
with respect to axes roughly parallel and normal to the rotor
thrust vector. The airfoil set rotating about axes normal to the
thrust vector impinges on the downwash from the rotor set, and
creates a reaction force vector tending to yaw the airframe right
or left depending on which way the set of airfoils is angled. The
second set of airfoils appears to function in a manner similar to a
tail rudder in a conventional aircraft, and therefore comes into
play when the device has developed significant forward speed, but
is less operative in yaw control when the helicopter is hovering at
a stationary point or otherwise has very low forward speed. In this
simplified system there is no need for cyclic blade pitch control,
and there is no collective pitch control. Tilt of the coaxial rotor
set, and increasing or decreasing the speed of the rotors, provides
pitch, roll and lift control.
SUMMARY
It has been recognized that simplifications in design, and the
weight and cost savings realized thereby, and commensurate
potential advantages in performance for the same cost, argue for a
further simplified propulsion and control system in a coaxial rotor
helicopter. The invention is directed to this end, and accordingly
provides a helicopter propulsion and control system configured for
actuating a helicopter airframe having a center of gravity
according to control inputs of an operator, comprising: a) a
counter-rotating rotor set tiltably coupled to the airframe, the
rotor set having an upward thrust vector; b) a power assembly
configured to actuate the counter-rotating rotor set, having a
center of gravity, and being fixedly coupled to the rotor set so as
to be tiltable therewith; and c) a control actuator operatively
coupled between the power assembly and the airframe to enable the
variable center of gravity of the airframe to move with respect to
the center of gravity of the power assembly, and with respect to
the thrust vector of the rotor set, whereby pitch and roll of the
airframe are controllable by the operator.
In a more detailed aspect, the invention further provides at least
one airfoil disposed so as to be in the downwash of said rotor set,
said airfoil cooperating with the downwash of the rotor set to
create a controllable sideways thrust vector. An airfoil control
actuator is operatively coupled between the airfoil and the
airframe, configured to change the orientation of the airfoil so as
to orient the sideways thrust vector according to control inputs of
the operator, whereby yaw of the airframe is controllable by the
operator. Two parallel airfoils can be used in tandem to minimize
their size, or two counter rotating airfoils can be used, each
being disposed on opposite sides of the airframe.
In another more detailed aspect, said power assembly further
comprises a prime mover and a gear set. The gear set divides power
output from the prime mover into two counter-rotating shafts to
drive the respective counter-rotating blades. The gear set can also
effect a reduction, whereby rotor rotational speed can be lower
than that of the prime mover. The gears can be arranged in
different ways, for example a planetary configuration or a beveled
configuration. In the latter case a single shaft rotation input,
and a dual coaxial counter-rotation shaft output oriented
orthogonal to the input can be provided. The prime mover can be any
suitable means of energy conversion, such as an internal combustion
engine, a turbomachine such as one of a number of turbine engines
conventionally used to power helicopters, and an electric motor.
The latter example is primarily used for smaller pilotless
aircraft, for example in inertially-guided and remote-controlled
controlled applications.
In a further more detailed aspect, in one embodiment the power
assembly is rotatable with respect to the airframe. In one
embodiment the power assembly has a single output shaft, and a
first rotor of the counter-rotating rotor set is attached to the
power assembly, rotating in a first direction, and a second rotor
of the counter rotating rotor set is attached to the single output
shaft, and rotates in the opposite direction.
As mentioned, in a further more detailed aspect the invention has
application in pilotless aircraft, which may be small, as well as
vehicles designed to carry a human operator. A pilotless system
where the operator remotely pilots the helicopter can further
comprise a transmitter and a receiver cooperating with: i) the
actuator(s) disposed between the airframe and the power assembly
and ii) an actuator controlling the position of the airfoil, and
iii) a power controller controlling rotor speed, to provide control
inputs. In another example the operator is a programable electronic
guidance and control system operatively connected to the power
controller and the rotor control and airfoil actuators, whereby the
helicopter is substantially self-controlled. In full-size
applications the operator pilots the helicopter onboard the
airframe, and in such systems the helicopter system further
comprises controls actuatable by the operator carried by the
airframe. Such controls can comprise for example a joystick or yoke
to provide control of pitch and roll, peddles to control yaw, and a
throttle to control rotor speed. A collective pitch control is not
required, as the magnitude of the thrust vector of the rotor set is
controllable solely by variation of the speed of rotation of the
counter-rotating rotor set. However, a collective pitch control can
be used in combination with motor speed to control lift in
applications where cost is of less concern. Differential collective
blade pitch control can be used to provide unbalanced torque in the
rotor set to provide yaw control input.
In another more detailed aspect, the actuator disposed between the
power assembly and the airframe can further comprise both a pitch
actuator disposed to tilt the rotor set and power assembly in a
first direction to control pitch, and a roll actuator disposed to
tilt the rotor set and power assembly in a second direction to
control roll.
Further details, features and advantages will become apparent with
reference to the following detailed description, taken in
conjunction with the accompanying drawings, which illustrate, by
way of example, the features of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevation view, partially in section, of a
helicopter in accordance with principles of the invention;
FIG. 2 is a top view, taken along line 2--2 in FIG. 1, of the
helicopter shown in FIG. 1;
FIG. 3 is a rear elevation view, taken along line 3--3 in FIG. 2,
of a portion of the helicopter shown in FIG. 2;
FIG. 4 is a top view, partially in cut-away, of a portion of the
upper rotor assembly of the coaxial rotor set of the helicopter
shown in FIG. 1;
FIG. 5 is a schematic side elevation illustration of a piloted
helicopter in accordance with principles of the present
invention;
FIG. 6 is a schematic side elevation view of a portion of the
helicopter as illustrated in FIG. 5 showing an alternative
arrangement;
FIG. 7 is a schematic side elevation illustration of a portion of a
helicopter in accordance with principles of the invention in
another embodiment;
FIG. 8 is a side elevation schematic illustration of a helicopter
in another embodiment in accordance with principles of the
invention; and
FIG. 9 is a side elevation schematic illustration of a helicopter
as illustrated in FIG. 8 in a different embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
With reference to FIGS. 1 and 2 of the drawings, which drawings are
provided for purposes of illustration, the invention is embodied in
a small pilotless helicopter 10 having an airframe 12 supported by
skids 14 while on the ground, and a coaxial rotor set 16 when
airborne. A prime mover in the form of an electric motor 18 powers
the helicopter through a reduction gear set 20, a sprag or
overrunning clutch 22 and bevel gear set 24. Power for the electric
motor comes from batteries 26 contained in a battery pack 28 slung
beneath, and carried by, the airframe 12.
A first set of rotor blades 30 are actuated by a first, or outer,
concentric drive shaft 32 through a first, or upper, bevel gear 34.
A second, or upper, set of rotor blades 36, is driven by a second,
or inner, drive shaft 38 connected to a second, or lower, bevel
gear 40. Power is transmitted to the first and second bevel gears
by a pinion gear 42 operatively connected to the overrunning clutch
22.
The bevel gear set 24 comprising the first 34 and second 40 bevel
gears and pinion gear 42, as well as the clutch 22, the motor 18,
and reduction gear set 20, together comprise a power assembly 44.
The power assembly further comprises a power assembly frame 46
which carries, supports, and aligns the various elements of the
power assembly. The power assembly is tiltably suspended from the
airframe 12 by a gimbal 48 bolted thereto. The gimbal is comfigured
to support the airframe in flight and provide relative rotation in
two axes (pitch and roll) between the airframe and the coaxial
rotor set.
The coaxial rotor set 16 is thereby fixedly connected to the power
assembly 44 so that they tilt as a unit with respect to the
airframe 12, as facilitated by the gimbal 48. A control actuator 50
tilts the power assembly and rotor set with respect to the airframe
in response to control inputs provided by an operator (not shown)
to provide pitch and roll control for the helicopter 10. The
control actuator, as will be further described below, connects the
airframe and the power assembly in such as way as to allow the
center of gravity of the airframe (and everything supported
thereby) to be shifted with respect to the power assembly and rotor
set. In this way, the center of gravity of the airframe, and
therefore of the helicopter as a whole, is shifted with respect to
a thrust vector comprising the force vector generated by the
rotation of the counter-rotating rotor set, and which generally
provides the lifting force on the helicopter. Therefore, pitch and
roll control is by weight shifting, as opposed to conventional
control by cyclic alteration of the pitch of the rotor blades 30,
36.
In further detail, the control actuator 50 in the illustrated
embodiment comprises a pitch actuator 52 which tilts the power
assembly and rotor set forwardly and rearwardly with respect to the
airframe through the gimbal 48 by pushing and pulling a pitch
linkage 54 connected to a hub 56 at the bottom of the power
assembly frame 46. In the illustrated embodiment the pitch actuator
is a servo 53 operatively linked to the pitch linkage 54 by a crank
58 having provision for adjustment of the control by selective
connection of the pitch linkage at one of several points along the
length of the crank giving rise to more or less pushing and pulling
motion for the same amount of rotation of the crank actuated by the
servo comprising the pitch actuator 52.
Control actuator 50 further comprises a roll actuator 60 comprising
a servo 61 which, like the pitch actuator 52, also turns a crank 58
with provision for adjustment. The roll actuator tilts the power
assembly 44 and rotor set 16 transversely, to provide roll control
by means of a first roll linkage operatively connected between the
crank 58 of the roll actuator 60 and a bell crank 64 rotatably
connected to the airframe 12, and a second roll linkage 66
operatively connected between the bell crank 64 and the hub 56. As
can be appreciated, the bell crank arrangement allows the pitch and
roll actuators to be disposed so as to be mounted together and move
linkages 54 and 62 in roughly parallel directions, yet provide
control inputs at orthogonal directions at the hub 56 at the bottom
of the power assembly. As will also be appreciated, pitch and roll
controls are independent, and can be applied separately or together
in controlling flight of the helicopter 10. A spring 68 is provided
between the hub 56 and the airframe 12 to eliminate any slop in the
control linkages so that pitch and roll control by the control
actuator 50 will be immediate and precise.
With reference to FIGS. 1, 2 and 3, the yaw control in the
illustrated embodiment is facilitated by an airfoil 70 which is
positioned in, and can be rotated in, the downwash from the
counter-rotating coaxial rotor set 16. As will be appreciated, this
is done to redirect air flow laterally, and thereby provide a
transverse thrust vector displaced from the center of gravity of
the helicopter 10 thereby tending to yaw the helicopter right or
left depending upon the direction of rotation of the airfoil. This
rotation is controlled by an airfoil control actuator 72. The
airfoil actuator further comprisises yaw actuator 74 comprising a
servo 75 having a crank 58 as described above. The crank is
connected by a yaw linkage 78 to a yaw control arm 78 integral with
an airfoil cuff 80 rotatably carried in a sleeve 82 mounted to the
airframe 12. In this way, the airfoil is carried by the airframe
and angled right or left by the yaw actuator 74. The airfoil
control actuator 72 further comprises adjustability in the yaw
control arm in the illustrated embodiment. Combined with
adjustability in the crank 58, yaw control can be made more
sensitive or less sensitive and a "neutral" position can be
adjusted to counteract any slight imbalance in the counter rotating
coaxial rotor set 16 tending to yaw the airframe right or left.
Adjustability of control sensitivity is also provided in pitch and
roll control by at least two means, one of which has to do with the
rotor set control actuator 50, which has adjustability in the
cranks 58 operatively connected to both the roll actuator 60 and
pitch actuator 52 of the rotor control actuator 50. The other has
to do with the coaxial rotor set 16, as will be discsssed
below.
With reference to FIGS. 1 and 2, control of the magnitude of the
thrust vector from the coaxial rotor set 16 is accomplished solely
by changing the speed of rotation of the rotor set. A power
controller 84 controls the speed of the motor 18, and thereby the
power delivered to the coaxial rotor set 16. The power controller,
as well as the control actuator 50 controlling the tilt of the
rotor set, and the yaw control actuator 72, are all operatively
electrically connected to a receiver 86 carried by the airframe 12.
The receiver further comprises an antenna 88. This allows an
operator (not shown) to control the helicopter 10 from a remote
location. A transmitter (not shown) unit includes operator
controls. Transmitter and receiver units for this application are
widely commercially available.
Further details of construction of the exemplary embodiment will
now be given. The first, or lower, set of rotor blades 30 are
attached to the first, or outer, drive shaft 32 by blade cuffs 90
comprising clevis pieces 91 attached to a rotor hub 92 connected to
the outer drive shaft 32 through a teetering hinge pin 94 disposed
substantially orthogonally to the longitudinal axes of the lower
rotor blades 30. The teetering hinge is located slightly above the
rotor hub, and accordingly the lower rotor set is under-slung.
The first or outer drive shaft 32 is supported by outer bearings 96
and a sleeve 98 attaching the power assembly frame 46 to the gimbal
48. A set of inner bearings 100 are disposed between the first or
outer drive shaft 32 and the second or inner drive shaft 38.
Another bearing 102 is disposed between the inner drive shaft and
the power assembly frame 46 at the lower end of the inner drive
shaft adjacent the hub 56. These bearings support the various
elements and allow rotation and counter rotation of the elements as
described therein.
With reference to FIGS. 1 and 4, details of connection of the
second or upper set of rotors 36 will now be described in more
detail. The upper rotors are attached to the second or inner drive
shaft 38 by rotor cuffs 104 comprising clevis pieces 105 attached
to an upper rotor hub plate 106. The upper rotors 36 are inclined
slightly upward, forming a coned rotor set, in contrast to the
lower rotors 30 which are horizontal. The angle of coning is about
2.5 degrees upward. Also, it should be noted that the upper rotors
are pitched less than the lower rotors to take into account the
fact that there is, in effect, an inflow from the upper rotor to
the lower rotor and accordingly for the two rotors to be
"balanced", so as not to induce rotation of the airframe, the lower
rotor must have more "bite." As an example, the upper rotors can be
inclined at about eight to twelve degrees, while the lower rotors
can be inclined at about eleven to fifteen degrees. In one
embodiment, adjustment means can be provided (not shown) to allow
fine adjustment of the relative pitch of the two rotors to balance
them. This can be by adjusting the pitch at the root of one or both
of the upper 36 and lower 30 rotors. Alternatively, or
additionally, adjustment tabs (not shown) can be provided on the
rotors, which are setable to have more or less pitch than the rotor
as a whole, to provide the fine adjustment in relative pitch
mentioned. The simplest arrangement is for relative pitch of the
upper and lower rotors to be "factory set" and require no further
adjustment.
Returning to discussion of the upper rotors 36 of the coaxial rotor
set 16, Bell stabilizer bars 108 and weights 110 are provided to
add stability to the upper rotor. By adding stability to the upper
rotor, the control response of the coaxial rotor set 16 is
affected. The distance 112 between the weights 110 is adjustable by
means of set screws (not shown) which can be loosened and the
weights moved and then the set screws are re-tightened. This allows
the response of the coaxial rotor set to control inputs to be
adjusted. For example, the stabilizer can be supplied with the
weights fully extended. The weights are then adjusted inwardly as
the operator (not shown) gains proficiency in controlling the
helicopter 10. This is the second means by which pitch and roll
control sensitivity can be adjusted, the first being in the control
actuator 50 discussed above.
Furthermore, it will be appreciated that the upper rotor can tilt
and teeter in two axes. The rotor hub plate is connected to a hub
sleeve 114 by pins 116, which allows the rotors to rotate
substantially about their longitudinal axes, providing feathering.
The hub sleeve is connected to the second or inner drive shaft 38
by a teetering pin 118 located slightly above the hub plate. This
provides an underslung rotor system. The teetering pin 118 is
located approximately at a position along a line connecting the
centers of gravity of the two upper rotors 36. The amount of
teetering provided can be adjusted by adjustment screws 120
disposed through the hub sleeve 114, as can best be appreciated
with reference to FIG. 1. This provides a stable rotor system.
With reference to FIG. 5, it will be appreciated that the
helicopter propulsion and control system previously described can
be embodied in a larger helicopter 150, being large enough to
accommodate a pilot 152. While the operative principles are
similar, the configuration of the aircraft is changed somewhat from
the pilotless vehicle discussed above. For example, a power
assembly 154 comprises an internal combustion engine or a
turbomachine 156 configured to function as the prime mover and
which supplies power to the counter-rotating coaxial rotor set 158.
Rather than batteries, a fuel storage tank 160 is provided. A gear
box 162 can contain bevel gears similar to those previously
described, and can also include reduction gearing. A clutch 164 can
be provided, as well as an additional reducing gear set 166,
particularly if the prime mover is of a type producing power at a
high r.p.m. The power assembly is, again, supported by a gimbal 168
which tiltably connects the power assembly 154 to the airframe 170.
A control actuator 172 which can further comprise separate pitch
and roll actuators (not shown) is operatively connected between the
airframe 170 and a hub 174 at the bottom of the power assembly as
before described. This arrangement allows pitch and roll control as
discussed above.
A yaw (or airfoil) actuator 176, supported by the airframe 170,
controls an airfoil 178. The airfoil is tiltable to control yaw as
discussed above.
A joystick 180 can be provided to facilitate pitch and roll
control. Pedals 182 can be provided for yaw control. A throttle
control (not shown) can be provided on the joystick, to enable fine
control of speed of the rotor set 158, thereby controlling lift.
Conventional avionics can be provided, with a display 184 provided
for convenience of the pilot 152.
With reference to FIGS. 5 and 6, in an alternative embodiment the
power assembly 154 can be oriented so that the output shaft of the
prime mover 156 is oriented parallel to drive shafts 186, 188
driving the counter rotating rotor set (not shown). In this
embodiment, a turbomachine is shown for the prime mover, and the
exhaust therefrom is directed by a controllable thrust diverter
190, so as to flow rearwardly, or to the right or left, thereby
supplementing yaw control provided by the airfoil 178. Linkages
192, 194 are connected at the bottom of the power assembly 154 to
the hub 174 and provide control inputs from the control actuator
(not shown) for pitch and roll control as discussed above. The
helicopter of this embodiment functions otherwise as discussed
above.
With reference to FIG. 7, in another embodiment of the invention in
a pilotless aircraft as described above (with reference to FIGS. 1
through 4) the helicopter 10 is modified so that the prime mover
200 of the power assembly 202 is directly coupled so as to rotate
with one of the rotors 204 of the counter-rotating coaxial rotor
set 206. More specifically, the outer drive shaft 208 is directly
coupled to the prime mover, and the two rotate together, driving
the lower rotor 204. The inner drive shaft 210 comprises an output
shaft from the prime mover, and drives the upper rotor 212. A power
assembly frame 220 is supported by a gimbal 222 and is actuated by
a hub 224 to tilt the power assembly and counter rotating rotor set
206 as previously described with respect to the pilotless
helicopter illustrated by FIGS. 1 through 4.
In the embodiment illustrated by FIG. 7, a sprag or overrunning
clutch 214 as described above is operatively connected only to the
inner drive shaft 210. Likewise, a reduction gear set 216, provided
if required, drives the inner shaft 210. Torque is transmitted to
the outer drive shaft 208 through casings of the elements of the
power assembly 202 (namely: the prime mover-in this case an
electric motor 200; the reduction gear set 216; and the sprag
214).
In the illustrated embodiment, the electric motor comprising the
prime mover 200 is a DC motor, and a commutator 218 is provided to
supply power to the motor. As can be appreciated, either one or two
disks can be used in the commutator, depending on whether the motor
casing and airframe both comprise a ground and are used as a
current path.
As can be appreciated, the concept of having the prime mover 200 of
the power assembly 202 rotate with one of the rotors 204 could be
implemented in a full size helicopter. For example, a radial piston
internal combustion engine (not shown), or a turbomachine (not
shown) can be adapted for such an implementation. Motor speed
control and thereby lift, can be controlled by throttling fuel
delivered to the prime mover through a rotating hub (not shown) and
such a helicopter would operate otherwise essentially as previously
described.
With reference to FIG. 8 of the drawings, in another exemplary
embodiment the invention can be incorporated in a pilotless
helicopter 230 which comprises a power assembly unit 232 comprising
an electric motor prime mover 234 a reduction gear set 236, a
clutch 238 as described above, and a gear box 240 configured for
dividing the power from the prime mover 234 between an inner drive
shaft 242 and an outer drive shaft 244. The gear box can be a
non-reducing bevel gear arrangement shown schematically, or it can
comprise a reducing or non-reducing planetary gear arrangement (not
shown).
The arrangements for the upper rotor 246 and lower rotor 248 are
otherwise as described above. The power assembly 232 is suspended
from the airframe 250 by a gimbal 252 as before described. A pitch
actuator 254 and roll actuator 256 comprise a control actuator
tilting the power assembly and counter rotating axial rotor set 258
with respect to the airframe as previously discussed. Also, a power
controller 260 is operatively connected to the electric motor
comprising a prime mover 234, and batteries of a battery pack 262,
as previously described, with a difference being that the power
controller is carried by the airframe rather than the power
assembly in this vertical configuration. A spinning prime mover
(not shown) directly coupled to one of the rotors can alternatively
be provided.
Another difference is that two airfoils 264, 266 are provided, each
actuated by airfoil or yaw actuators 268, 270 respectively. In this
illustrated embodiment, the airfoils are disposed "fore and aft",
and tilt in opposite directions to provide a balanced force
reaction fore and aft, and to provide a rapid response to yaw
control input. A receiver 272 and antenna 274 are operatively
connected to all control elements, so that control inputs from a
remote operator (not shown) are translated into motions of the
aircraft.
Turning now to FIG. 9, in another embodiment an outer protective
enclosure 280 can be provided, cofigured to enclose the
counter-rotating coaxial rotor set 258 of a pilotless helicopter
230, such as that described above with reference to FIG. 8. The
protective enclosure comprises an upper portion 282 having openings
configured for admitting air for intake into the counter-rotating
coaxial rotor set 258. The enclosure also includes a lower portion
284 which includes openings allowing downwash from the rotor set to
escape from the enclosure, thereby facilitating lift of the
helicopter 230. A mesh configuration having low resistence to
airflow can be used.
A power assembly 286 can be provided, which is of the kind
described above in connection with FIG. 8, or which has a rotating
prime mover directly coupled to one of the rotors of the counter
rotating rotor set 258 (such as described above in connection with
FIG. 7). As will be appreciated, the pilotless helicopter 230 shown
in the embodiment of FIG. 9 can be operated indoors, or in other
situations where the rotors need to be protected from the
environment and vice-versa. Also, in this embodiment the airfoils
264, 266 are at least partially hidden within the protective
enclosure, and this and other elements of the pilotless helicopter
230 can thereby be at least partially hidden from view. This can be
used to alter the appearance of the aircraft, and disguise its true
nature and/or operative features. Accordingly, visual effects, such
as making the pilotless helicopter appear as a "flying saucer," can
be achieved.
While several particular forms of the invention have been
illustrated and described, it will also be apparent that various
modifications can be made without departing from the sprit and
scope of the invention.
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